A pilot project to eradicate giant wild rhubarb (gunnera tinctoria) is gaining momentum.
Invasive alien terrestrial species such as gunnera are a major problem, causing environmental harm in different parts of Ireland. They are taking over vast areas of agricultural land by excluding native species and are one of the biggest threats to biodiversity worldwide.
A pilot programme was launched in Achill, Co. Mayo, this year to rid the island of the plant, and they are now looking to expand it with an appeal to more landowners to join the fight.
Under the programme to eradicate or at least control gunnera, and to a lesser extent Japanese knotweed, in upper Achill, agreement was reached that the best approach was to use a knapsack sprayer and spray these plants. All landowners in upper Achill were encouraged to spray their land as it is important that all land be sprayed to ensure it will not be a source of cross-contamination and spread to other fields in future years.
Gunnera was introduced into Achill over 100 years ago as an ornamental plant (most likely) and then spread as an invasive species. Gunnera is native to countries like Chile, where there is a similar climate to the west of Ireland.
It grows on peaty soils (not on bogs), river banks, gravely road sides and on cliffs. It also thrives where the land is not grazed or where it is unused. Gunnera has spread rapidly in upper Achill owing to emigration and the closure of houses. It is estimated that there are over 170 acres of land under gunnera on the island.
Its ability to grow on marginal soils is attributed to the fact that the plant can ‘fix’ its own nitrogen from the atmosphere, which in turn gives it a lush green appearance in the spring and the ability to outcompete other plants like grasses.
Consent was received from most landowners in the upper Achill area (Sraheens/Kildownet) to gain entry to their land for spraying purposes. A small number of landowners have sprayed their own land since the start of the campaign. However, more landowners are being encouraged to spray their land.
Approximately five to six acres of infected/overgrown land has been treated in the Sraheens area and there was a good response to the herbicide application.
The gunnera plants (over 2m in height) were so dominant in the fields in Sraheens that it was nearly impossible to enter some parcels of land for spraying purposes. Those plants that were sprayed in July did not produce any large fruiting heads compared to the fields which were not sprayed.
This is a long term (five to 10-year) project where annual monitoring for any regrowth is essential. Undoubtedly, re-spraying will be required since each plant can produce over 250,000 seeds/plants.
Other villages in upper Achill are being urged to take up the mantle and volunteers are needed to organise campaigns like the one in Sraheens, where good progress was made during 2015.